Many powered trimmers of various designs have been developed and commercialized for use by an operator in cutting or trimming vegetation such as grass, weeds, and brush. In a typical configuration, an example of which is disclosed in U.S. Pat. No. 5,077,898 to Hartwig, the powered trimmer includes a motor powered by electricity or a combustive fuel such as gasoline or a gasoline/oil mixture. The motor typically provides rotational driving power to a cutting mechanism that includes one or more cutting cords of nylon or metal or a set of cutting blades. The motor and cutting mechanism are mounted to an elongate boom that is held by the operator during use of the trimmer. Typically, the trimmer is balanced by mounting the motor and cutting mechanism at opposite ends of the boom. This configuration requires that a drive shaft be disposed within the length of the boom to interconnect the rotating output component of the motor with the rotating cutting mechanism. To enable the operator to comfortably wield the trimmer in an upright standing or walking position, the cutting mechanism is often situated at an angle in relation to the motor and/or the boom. Accordingly, a angled gear case or trimmer head is commonly interposed between the boom and the cutting mechanism, with the drive shaft of the boom connected to one end of the gearing of the gear case and the cutting mechanism connected to an output shaft extending from the gear case.
During operation of a typical trimmer such as described hereinabove, as the cutting mechanism rotates, its cords or blades cut through the targeted vegetation and throw clippings outwardly. Moreover, the cutting mechanism often encounters objects such as rocks, pieces of wood, and other debris, which can also be thrown by the cutting mechanism. To protect the operator of the trimmer from injury inflicted by clippings and objects thrown by the cutting mechanism, it is common for trimmers to include a shroud or guard mounted to the gear case or boom so as to shield the operator from the thrown objects. Most clippings guards are positioned only in the frontal area between the cutting mechanism and the operator, as disclosed in aforementioned U.S. Pat. No. 5,077,898. Other clippings guards are designed to completely surround a portion of the cutting mechanism as disclosed in U.S. Pat. No. 6,260,278 to Faher, or to surround the entire cutting mechanism as disclosed in U.S. Pat. No. 6,301,788 to Webster.
It can be appreciated by persons skilled in the art that while guard structures have thus been provided to protect the operator of the trimmer from clippings and other matter cut or thrown by the cutting mechanism, trimmers have in the past failed to provide any guarding means for preventing clippings from contacting the output shaft of the gear case or trimmer head. It is well-known that clippings, and even blades of grass that have yet to be cut, have a strong tendency to wrap around the exposed portions of this output shaft as the output shaft rotates, or otherwise to become bound to or contact the output shaft. Such contact between vegetative matter and the output shaft can have a number of deleterious effects. For example, the bound vegetative matter can impede rotation of the output shaft, causing damage or premature wear of the gearing and motor provided with the trimmer. Moreover, an accumulation of vegetative matter on the output shaft can interfere with the performance of the cutting mechanism in uniformly cutting targeted areas of vegetation and effectively clearing clippings from the immediate vicinity of the cutting elements, especially in the case of nylon cords. Additionally, the binding of vegetative matter increases the frequency of maintenance required for the trimmer, such as cleaning, as well as the time required to perform maintenance.
In view of the foregoing, it would therefore be advantageous to provide a power trimmer with a shield apparatus for preventing or at least minimizing contact between vegetative matter and the output shaft of such trimmer.